This invention relates to the identification of defective fuel assemblies in liquid-metal-cooled fast breeder reactors. In more detail, the invention relates to apparatus for separately interrogating the fuel assemblies of a liquid-metal-cooled fast breeder reactor for a signal indicative of the presence of a failed fuel element therein. Specifically, the invention relates to an improvement in the Experimental Breeder Reactor No. 2 (EBR-II) whereby existing fuel handling equipment can be used to interrogate each subassembly in turn to determine whether a failed fuel element is present therein. EBR-II is described in ANL-5719 and addendum thereto, the Hazard Summary Report for the EBR-II, and the fuel unloading machine therefor is described in ANL-7201 and ANL-7585.
Since it is inevitable that cladding failures releasing fission gases to the coolant will occur during operation of fast breeder reactors and under certain conditions a clad rupture may dictate reactor shutdown so that the source can be removed from the active reactor core, identification of the subassembly having the cladding failure is essential. Operational possibilities for leak detection include
1. Cover gas analysis
A. Gamma analysis PA1 B. Electrostatic discrimination PA1 C. Xenon tagging PA1 A. Gamma analysis of sparge gas PA1 B. Delayed neutron analysis PA1 1. 3,663,363 - Crouthamel et al. - Xenon Tagging PA1 2. 3,234,101 - Berthod - A funnel is used to pick up an entraining gas which has picked up fission gases. PA1 3. 3,453,867 - Webb et al. - Detecting means within the fuel assembly is used to detect fission gas in a funnel. PA1 4. 3,575,802 - Gelius - Employs a fuel handling machine to assist in sampling coolant from fuel subassemblies sequentially and PA1 5. 3,612,860 - Hackney - Sequentially tests samples of coolant from individual fuel assemblies.
2. Sodium analysis
Specific U.S. Pat. Nos. on leak detection include
Unfortunately, the identification of a failed subassembly in a reactor containing many fueled subassemblies using these known techniques is quite difficult, time-consuming and expensive.